In recent years, magnetic disk devices, including hard disk drives, have been strongly required to have much higher capacity than before. A shingled write recording method has been attracting attention as one solution. In this method, in a write operation, the track pitch is narrowed and data is written so as to overwrite a part of an adjacent track. When the track pitch gets narrower than a specific value as the result of an increase in overlapping, the leakage of magnetic field from adjacent tracks (i.e., inter-track interference) in a read operation becomes too large and therefore the quality of the reproduced signal deteriorates significantly. To alleviate the inter-track interference, a reproduction technique for using signal information on adjacent tracks as noise-canceling information in reproducing the present track has been proposed (e.g., Masaaki Fujii, “Iterative ITI Canceller for Shingled Write Recording,” presented at the 2010 Institute of Electronics, Information and Communication Engineers Electronics Society Convention).
With this technique, it is necessary to subtract information for canceling inter-track interference obtained from adjacent track information from information on the present track. To subtract the former from the latter properly, subtraction has to be done after the bit positions of an adjacent track are aligned with those of the present track.
However, in magnetic disk devices before the advent of the shingled write recording method, there was a large difference in bit position between a track and an adjacent track. It was difficult to align the bit positions of the preceding track with those of the present track.
In the conventional magnetic disk device, there is a difference in bit position between a track and an adjacent track.